Device for photogrammetrically surveying an object in which a reference pattern is arranged outside sensor imaging beam paths

ABSTRACT

In a device for photoqrammetrically surveying an object using a number of sensors which can be positioned individually with respect to the object, position of the sensors (5, 6, 7) an optical reference pattern records the respective positions of the sensors. The optical reference pattern is arranged outside the imaging-beam paths of the same in defined spatial position in absolute terms and is imaged via optical deviating means by means of sensors. Arranging the reference pattern (14) outside the imaging-beam paths gives greater freedom regarding the capability of positioning the sensors with respect to arranging the reference pattern on the object.

BACKGROUND OF THE INVENTION

The invention relates to a device for photogrammetrically surveying anobject. Such devices are typically used for surveying motor vehicles, asdiscussed the paper "Fotogrammetrische Vermessung von Kraftfahrzeugen"(Photogrammetric surveying of motor vehicles) in ATZ 91 (1989) 6. In thecase of this known device, surveying the object concerned is performedin such a way that photos of the object are taken as it were from anumber of directions by means of at least two cameras containing thesensors and are evaluated in a computer; said computer supplies adigital data record, which precisely describes the dimensions of theobject.

However, a prerequisite for achieving a satisfactory measurement resultis that the spatial position of the sensors, i.e. of the cameras,relative to one another and relative to the object, i.e., the so-calledouter orientation, and the position of the objectives lenses relative tothe sensors assigned to them, the so-called inner orientation of themeasuring equipment (cameras), are precisely known. This problem ofouter orientation is particularly prominent when the sensors can bepositioned individually, i.e., independently of one another, as a resultof which a better adaptation of the imaging-beam paths to the respectiveobjects in comparison with a fixed coupling of the sensors is possible.

According to the cited prior art, the inner and/or outer orientation isperformed by there being arranged in the object space reference systems,for example graduated scales, which thus form as it were referencepatterns in a spatial position which is defined in absolute terms andare imaged by means of the sensors as well as stored. The storedreference patterns are then taken into consideration by the computer inthe evaluation of the images of the object supplied by the sensors.

SUMMARY OF THE INVENTION

The invention is based on the object of designing a device of thegeneric type in such a way that the positioning of the sensors, that isto say in the final analysis of the cameras also containing theperspective centers, relative to the object is not affected by theimaging of the reference pattern.

It is essential for the invention that although the reference pattern isarranged in a defined, fixed spatial position, it is outside theimaging-beam paths of the sensors, so that when positioning the sensorsrelative to one another and relative to the respective object there isno need to consider the accommodation of the reference pattern in thesebeam paths. The imaging of the reference pattern by means of the sensorsis performed using optical deviating means, for example partiallytransmitting mirrors or prisms in the imaging-beam paths of the sensors.It is then possible to arrange a reference pattern, assigned to all thesensors, for example also relatively far away from the object and forexample to cast a mirror image of this reference pattern onto all thesensors. In the case of a direct imaging of the reference pattern, saidpattern would have to be arranged in the area of the object, whichpresents difficulties in particular in the case of small objects ofwhich the shape is to be recorded exactly by the device.

BRIEF DESCRIPTION OF THE DRAWINGS

An illustrative embodiment of the invention is explained below withreference to the figure, which schematically shows a device containingthree sensors.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The object to be surveyed is denoted by 1. Arranged around it indiffering spatial position are three cameras 2, 3 and 4, which in eachcase contain as essential component parts a sensor 5, 6 and 7 as well asan objective lens 8, 9 and 10. The imaging-beam paths of the individualcameras or sensors are denoted by 11, 12 and 13. As is evident, thecameras 2, 3 and 4 can be positioned individually, i.e independently ofone another, with respect to the object 1, so that their position can bechosen with regard to the optimum surveying of the respective object.

Not shown, since known with respect to its structural design, is a dataprocessing unit, connected to the sensors 5, 6 and 7, for evaluating theobject images supplied by the individual sensors; as already stated atthe beginning, this data processing unit supplies a digital data record,which describes the spatial form of the object.

For an accurate surveying of the object 1, exact recording both of theposition of the objectives 8, 9 and 10 relative to the sensors 5, 6 and7 assigned to them, i.e. the inner orientation of the cameras 2, 3 and4, and the spatial position of the cameras 2, 3 and 4 relative to oneanother as well as relative to the object 1 is necessary. For reasons ofthe accuracy required, the recording of these spatial positions isperformed not by mechanical means, that is to say for example by meansof scales on adjusting mechanisms for the cameras, but optically byimaging of the optical reference pattern 14, which is located in adefined spatial position in absolute terms. This optical referencepattern is typically in the form of concentric circular marks, as shown.In this illustrative embodiment, for this purpose there are arranged inthe imaging-beam paths 11, 12 and 13 partially transmitting mirrors 15,16 and 17 (the first within the camera 2, the two others outside thecamera 3 or 4 assigned to them), which are aligned in such a way thatthey cast mirror images of the reference pattern 14 onto the sensorsurface of the camera concerned according to the respective position andalignment of the latter. It goes without saying that the mirrors 15, 16and 17 must have an exact, defined position with respect to therespective sensor surface 5, 6 and 7, so they are firmly connected tothe respective camera 2, 3 and 4.

As indicated in the case of the camera 2 by the position of thepartially transmitting mirror 15, the latter need not lie as it wereoutside the camera, that is to say outside the distance betweenobjective 8 and object 1, but can also be arranged in the distancebetween sensor 5 and objective 8, there then being provided, ifappropriate, an additional objective 18 in the camera housing. Thepossibility then exists of approaching very close to the object 1 withthe camera 2.

Consequently, the invention provides a device of the generic type whichallows accurate surveying of different objects without affecting thecapability of positioning the sensors with respect to the object.

I claim:
 1. A device for photogrammetrically surveying an object,comprising:at least two individually positionable optical sensors; anobjective lens associated with each of said optical sensors in a definedspatial relative position; an optical reference pattern, arranged on theobject space side of said optical sensors in a known, fixed spatialposition, for detecting at least one of the following positions bydirecting said reference pattern onto said sensors;the position of saidobjective lens with respect to its associated sensor, the position ofsaid sensors relative to one another, and the position of said sensorswith respect to said object; and optical deviating means associated witheach of said sensors and in a defined position with respect to itsassociated sensor, for directing said reference pattern, wherein saidoptical reference pattern is arranged outside the imaging-beam paths,running between said object and said sensors.
 2. A device according toclaim 1, wherein said optical deviating means are at least partiallytransmitting and are located in said imaging-beam paths.
 3. A method forphotogrammetrically surveying an object, comprising the stepsof:arranging an optical reference pattern on the object space side of atleast two individually positionable optical sensors in a known, fixedposition outside the imaging beam paths running between said object andsaid sensors; deflecting said optical reference pattern onto saidsensors; and detecting at least one of the following positions;theposition of an objective lens associated with each sensor, the positionof said sensors relative to one another, and the position of saidsensors with respect to said object.